Color filters are essential components of solid-state image sensors and liquid crystal displays. Improvement in color separation and improvement in color reproducibility are required for a color filter for a solid-state image sensor, in particular.
These color filters have a colored region with multiple hues (that is, a colored cured film), and usually have colored regions of at least red, green, and blue colors (hereinafter, may be referred to as “color patterns”, or “colored pixels”). A method for forming such a color patterns is as follows. First, a colored radiation-sensitive composition containing any of red, green and blue colorants are applied by coating to provide a first hue, and the colored radiation-sensitive composition is then exposed to light and developed, and subjected to a heat treatment as needed, to form a color pattern having the first hue. Next, similar coating, exposure and development processes, and a heat treatment as needed, are repeated with respect to a second hue and a third hue, respectively.
As a colorant used for a color filter, pigments are widely used since they have a vivid tone and high coloring power. In particular, a pigment which is micronized and exhibits suitable color separation properties is preferably used.
Recently, for solid-state image sensors, colored pixels with reduced size (for example, a color pattern having a side length of 1.0 μm or less) have been sought after for the purpose of improving resolution. However, it is known that, in solid-state image sensors, deterioration caused by noise is associated with the reduction in size of colored pixels.
A solid-state image sensor is used as an optical sensor for a variety of purposes.
For example, since near-infrared light has a longer wavelength than visible light and thus tends not to scatter, it can be utilized for distance measurement, three-dimensional measurement, and the like. In addition, since near-infrared light is invisible to humans, animals and the like, it is not noticed by subjects even when the subject is illuminated with a near-infrared light source at night. Therefore, near-infrared light can be used to take photos of nocturnal wild animals, as well as to photograph persons without provoking them for security purposes. Optical sensors detecting such near-infrared light can be developed for various purposes, and thus there has been a persistent desire to develop a color filter that can be used for solid-state image sensors that detect near-infrared light.
As a colored composition for producing a color filter having similar spectral characteristics to that of a color filter for near-infrared sensors, a red colored composition containing C.I. Pigment Violet 23, a yellow pigment, and a red pigment is known (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2007-138135). Although this composition is effective for illuminance sensors, it also has sensitivity in the red region. In addition, this composition does not enable favorable pattern formation by UV light exposure, since light in the UV region is blocked. Thus, for near-infrared sensors, further improvements in the spectral characteristics and pattern formability of the composition are required.
In addition, a light-shielding photosensitive resin composition that transmits light in the ultraviolet region and exhibits improved pattern formability has been proposed (for example, see JP-A No. 7-28236). This composition, however, exhibits insufficient light-transmission properties in the near-infrared region, so that it has not been useful for near-infrared sensors.